Our hypothesis is that a colonic delivery system (CDS) is effective in delivery of pyridostigmine bromide to the colon, thereby accelerating the colonic transit of solid residue. Our specific aims are to evaluate the dose-related effects of pyridostigmine bromide (5, 10, 20 mg) compared to placebo delivered via a colonic delivery system on colonic transit time, particularly on the rate of emptying of the ascending and transverse colon; and to assess the bioavailability of pyridostigmine bromide delivered by means of a colonic delivery system.